Well, this is embarassing. I was all ready to solder in the replacement resistors I'd mentioned in another thread (Rs, Rf, R3, and mute resistor), into my Chipamp.com LM3886 boards, when I discovered I bought the wrong replacements.
I bought 1/4W for R2, Rf and R3, but they're too big.

Can anyone tell me What wattage/physical size are the resistors in those locations by default. Yet another thing that is not in the Chipamp.com manual.

The resistors around an LM3886 can be 250 mW or 400 mW types. The only two that need to be higher power are the resistor in the Zobel network (R+C from the output to ground) and in the Thiele network (L||R in series with the output). Those two resistors need to be 2 W types. I don't recall if the chipamp.com boards have Zobel or Thiele networks.